JP7151163B2 - Composite material - Google Patents

Description

The present invention relates to composite materials.

Various studies have been made on fiber-resin composite materials. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes a composite panel composed of a foam structure (core material) and a carbon fiber reinforced composite material arranged on the surface thereof (Fig. 1 of Patent Document 1). Further, it is described that a cured carbon fiber reinforced composite material is arranged on both upper and lower surfaces of the core material via an adhesive (Patent Document 1, paragraph 0068).

JP 2006-76366 A

As a result of investigation by the present inventor, it was found that the composite material described in Patent Document 1 has room for improvement in lightness and mechanical strength.

According to the findings of the present inventors, when the foam structure described in Patent Document 1 and the carbon fiber reinforced composite material are directly bonded without using an adhesive from the viewpoint of weight reduction, the interface between these surfaces It was found that the adhesive strength in the composite decreased, resulting in a decrease in the mechanical strength of the composite as a whole.

As a result of examining the bonding structure based on such knowledge, it was found that an anchor effect was obtained by allowing the resin in one fiber-reinforced resin material to penetrate from the surface of the other non-woven fabric to the inside, and the fiber-reinforced resin material and the non-woven fabric. It was found that the adhesive strength at the interface with can be increased.
As a result of further investigation, we used a wall portion, a lightweight portion, and a core member. The inventors have found that the formation of the recessed region improves the mechanical strength while maintaining the lightness of the composite material, and has completed the present invention.

According to the invention,
a core member having a layered structure;
A composite material comprising a support plate member laminated on one surface of the core member and made of a fiber-reinforced resin material in which reinforcing fibers are impregnated with a resin,
The core member has a wall portion and a light portion having a smaller specific gravity than the wall portion,
The wall portion has a nonwoven fabric composed of a plurality of fiber fillers from the one surface of the core member to the other surface opposite to the one surface, and
A composite material is provided comprising an impregnated region in which a portion of the resin in the fiber reinforced resin material impregnates the nonwoven of the wall.

ADVANTAGE OF THE INVENTION According to this invention, the composite material excellent in light weight and mechanical strength is provided.

(a) It is a top view which illustrates the structure of the composite material of this embodiment. (b) is a sectional view taken along line aa of (a); (c) is an enlarged view of the α region of (b). 1 is a schematic perspective view illustrating the configuration of an expandable paper product; FIG. It is a cross-sectional process drawing which illustrates the manufacturing method of an expandable papermaking body. It is a cross-sectional process drawing which illustrates the manufacturing method of a foam (formed body of an expandable paper-making body).

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to actual dimensional ratios. In this embodiment, the front, back, left, right, up and down directions are defined as shown in the drawings. However, this is defined for convenience in order to simply explain the relative relationship of the constituent elements. Therefore, there is no limitation to the orientation during manufacture or use of the product embodying the present invention.

The composite material of the present embodiment includes a core member having a layered structure, and a support plate member laminated on one surface of the core member and made of a fiber-reinforced resin material in which reinforcing fibers are impregnated with resin. It is. The core member has a wall portion and a light portion having a smaller specific gravity than the wall portion, and the wall portion extends from one surface of the core member to the other surface opposite to the one surface and is made of a plurality of fiber fillers. It has a nonwoven fabric composed of: Such a composite material has an impregnated region in which part of the resin in the fiber-reinforced resin material permeates into the nonwoven fabric of the wall.

According to this embodiment, the wall portion, the lightweight portion, and the core member are used, and the wall portion of the core member having the lightweight structure is soaked with a portion of the resin in the fiber-reinforced resin material that has penetrated into the nonwoven fabric. By forming the recessed region, it is possible to realize a structure of a composite material having excellent mechanical strength while maintaining light weight.

In the composite material of the present embodiment, by adopting a core member having a wall portion and a light portion having a lower specific gravity than the wall portion, a structure excellent in weight reduction can be realized, and the core member having the wall portion has a fiber structure. By stacking support plate members made of reinforced resin material, a structure with excellent mechanical strength can be realized.

According to this embodiment, a wall having a nonwoven fabric in which a plurality of fiber fillers are oriented substantially parallel to one surface perpendicular to the lamination direction of the core member and the support plate member, that is, one surface of the core member. By using the part, it is possible to further improve mechanical strength such as impact strength in the lamination direction while maintaining lightness in the composite material.

The composite material 100 of the present embodiment can be used, for example, for aircraft, automobile parts, electronic device housings, building (container) wall materials, and the like.

Each element of the composite material of this embodiment will be described.

As shown in FIGS. 1(a) and 1(b), the composite material 100 of this embodiment includes a core member 110 having a layered structure and a support plate member 120 laminated on the lower surface 116 of the core member 110. . As shown in FIG. 1B, the composite material 100 has a sandwich structure in which support plate members 120 and 122 are laminated on each of the lower surface 116 (one surface) and the upper surface 118 (surface opposite to the one surface) of the composite material 100. can have

The composite material 100 may be composed of at least a two-layer structure of the core member 110 and the support plate member 120, and as shown in FIG. It may consist of a three-layer sandwich structure. With this two-layer structure or three-layer sandwich structure as a basic structure unit, the composite material 100 may have a repeating structure of a plurality of basic structural units. In this case, the basic structural units may be the same or different. In the laminated structure of the composite material 100, a plurality of basic structural units may be formed continuously, or may be formed via other functional layers such as a cushion layer and an adhesive layer.

The composite material 100 may have a sheet-like structure as shown in FIG. 1(b), but may have various three-dimensional structures depending on the purpose.
When viewed in a direction perpendicular to one surface of the support plate member 120, the shape of the composite material 100 in top view can be various shapes such as a rectangular shape, a polygonal shape, a circular shape, a curved shape, or a combination thereof. can have On the other hand, the cross-sectional shape of the composite material 100 when viewed in the stacking direction of the support plate member 120 and the core member 110 is, for example, a rectangular shape, a polygonal shape, a circular shape, a curved shape, or a curved shape in FIG. It can have a variety of shapes, such as combinations of these. In the case of the composite material 100 having a three-dimensional structure, for example, the lower surface 116 of the core member 110 may be arranged to face one surface of the support plate member 120 having the three-dimensional shape.

In addition, when the composite material 100 includes a plurality of core members 110, they may be configured with the same or different members. Also, when the composite material 100 comprises a plurality of support plate members 120, 122, each may be composed of the same or different members.

The respective thicknesses of the composite material 100, the core member 110, and the support plate members 120 and 122 can be appropriately set according to the application.

[Support plate member]
Next, the configuration of the support plate member will be described.
The support plate members 120 and 122 can be made of a fiber-reinforced resin material in which reinforcing fibers are impregnated with resin. As the support plate members 120 and 122, as shown in FIG. 1B, a sheet-like fiber-reinforced resin material having two main surfaces, an upper surface and a lower surface, can be used. The support plate members 120 and 122 may be composed of a single layer of fiber-reinforced resin material, or may be composed of two or more laminated layers of fiber-reinforced resin material.

Thermosetting resins and thermoplastic resins are examples of resins used for the fiber-reinforced resin material.
Examples of thermosetting resins used for the fiber-reinforced resin material include phenol resins, epoxy resins, bismaleimide resins, melamine resins, and urethane resins.
Examples of thermoplastic resins used for the fiber-reinforced resin material include polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyamide, polyetherketone, polyetheretherketone, polysulfone, and polyphenylene sulfide.
These may be used alone or in combination of two or more. Among these, thermosetting resins are preferred from the viewpoint of mechanical strength or chemical resistance, and phenol resins, epoxy resins, and bismaleimide resins can be used. Epoxy resins can also be used because they can be used in a wide range of applications.

The reinforcing fibers used in the fiber-reinforced resin material can be composed of a woven fabric (fiber cloth) or a non-woven fabric. Examples of the reinforcing fibers include organic fibers, inorganic fibers, and metal fibers. Specifically, synthetic fibers such as polyamide fiber, aramid fiber, polyimide fiber, polyparaphenylene benzoxazole fiber, polyarylate fiber, ultra-high molecular weight polyethylene fiber, high-strength polypropylene fiber, acrylic fiber, phenol fiber, carbon fiber, etc. organic fibers; inorganic fibers such as glass fibers, ceramic fibers, rock wool, potassium titanate fibers and basalt fibers; metal fibers such as stainless steel fibers, steel fibers, aluminum fibers, copper fibers, brass fibers and bronze fibers. These may be used alone or in combination of two or more.
Among these, aramid fiber, carbon fiber, and the like can be used from the viewpoint of mechanical strength and weight reduction. Glass fibers can also be used from the viewpoint of moldability, uniformity of molded products, and abrasion resistance.

Further, as the reinforcing fibers used in the above-mentioned fiber-reinforced resin material, those which have undergone surface treatment in advance may be used for the purpose of enhancing adhesion to the resin. Examples of the surface treatment method include coupling agent treatment, oxidation treatment, ozone treatment, plasma treatment, corona treatment, and blast treatment. Among these, a coupling agent treatment can be used.

Moreover, the fiber-reinforced resin material may contain other components in addition to the resin and reinforcing fibers described above, depending on the purpose. Examples of other components include curing agents, curing aids, fillers, releasing agents, coupling agents, flame retardants, and coloring agents such as carbon black.

Next, a method for manufacturing the support plate members 120 and 122 will be described.
An example of the method for manufacturing the support plate members 120 and 122 is a step of impregnating reinforcing fibers with a resin composition containing the above resin and, if necessary, other components to form a fiber-reinforced resin material. can include This fiber-reinforced resin material is used as the support plate members 120 and 122, and can be, for example, in the form of a roll that can be wound up, or in the form of a sheet such as a sheet having a rectangular shape.
Further, when the resin composition in the fiber-reinforced resin material contains a thermosetting resin, after impregnation, the resin composition (thermosetting resin composition) is heated until it reaches a semi-cured state (B-stage state). and a drying step of drying.

In the present embodiment, known impregnation means include, for example, a method of dissolving a resin composition in a solvent to prepare a resin varnish and immersing the reinforcing fibers in the resin varnish, and applying the resin varnish to the reinforcing fibers using various coaters. a method of spraying the resin varnish onto the reinforcing fibers by spraying; and a method of laminating a resin film (resin film) made of a resin composition on one side or both sides of the reinforcing fibers. In addition, the resin film may be a paper product (paper prepreg) obtained by drying a paper layer formed by a paper making method.

[Core member]
Next, the configuration of the core member will be described.
The core member 110 can have a layered structure having a wall portion 112 and a lightweight portion 114 lighter than the wall portion 112, as shown in FIG. 1(b).

When the core member 110 is viewed from the upper surface 118, the lightweight portion 114 is configured by a space partitioned by the wall portion 112, as shown in FIG. 1(a). Thereby, it is possible to increase the mechanical strength of the core member 110 . In addition, since the core member 110 can be provided with a plurality of lightweight portions 114, weight reduction can be achieved.

The wall portion 112 is formed over the entirety of the core member 110 from the lower surface 116 (one surface) to the upper surface 118 (the other surface opposite to the one surface). That is, in a cross-sectional view of the core member 110 , the wall portion 112 can cover the entire circumference of the side wall surface side of the lightweight portion 114 . Thereby, the mechanical strength of the core member 110 can be improved. On the other hand, since the two adjacent light weight portions 114 can form side walls with the common wall portion 112, the weight of the core member 110 can be reduced.

A part or the whole of the light weight portion 114 may be composed of a void portion or a foam portion. The foamed portion is made of a foamed member, and when the wall portion 112 has a foamed structure, the foamed portion is made of a foamed member having a higher foaming rate than that of the wall portion 112 . By configuring the lightweight portion 114 to have a smaller specific gravity than the wall portion 112, the weight reduction of the core member 110 can be improved.

When viewed from a direction perpendicular to the top surface 118 of the core member 110, the wall portion 112 may have a honeycomb structure as shown in FIG. 1(a). This makes it possible to reduce the weight and improve the mechanical strength. In addition, the shape of the wall portion 112 when viewed from the upper surface 118 of the core member 110 can be various shapes other than the honeycomb structure. It can have a variety of shapes, such as combinations of these. These may be used alone or in combination of two or more.

The wall portion 112 may comprise a non-woven fabric composed of a plurality of fibrous fillers.
The nonwoven fabric in the wall portion 112 can have a structure in which a plurality of fiber fillers are oriented substantially parallel to the lower surface 116 of the core member 110, as shown in FIG. 1(b). In this specification, the term "substantially" means that it includes a range that takes account of manufacturing tolerances, variations, etc., unless otherwise explicitly stated. As a result, the resistance to impact from the stacking direction of the core member 110 and the support plate member 120 can be increased, so that it is possible to realize a structure that improves the mechanical strength while reducing the weight.

The wall portion 112 of the core member 110 is, as shown in FIG. A loading region 130 is provided. Thereby, the bonding strength between the support plate member 122 and the core member 110 can be increased. Since addition of an adhesive for bonding between members is not required, it is possible to realize a joint structure that improves the mechanical strength of the composite material 100 while maintaining lightness.

Part of the resin in the fiber-reinforced resin material migrates into the nonwoven fabric when heated. As the resin in the fiber-reinforced resin material, as described above, a resin such as a thermoplastic resin or a B-stage thermosetting resin that can be partially moved by heating is used. As the heating, a heat treatment or the like in the process of laminating the support plate member 122 and the core member 110 is used. This creates a seepage region 130 in the wall 112 of the core member 110 . The resin in the infiltration region 130 is entangled with a plurality of fiber fillers and permeates so as to involve the diameter circumference of the fiber fillers. By pressing the support plate member 122 and the core member 110 while heating them in this manner, a strong joint structure can be substantially reduced.

The infiltration depth of the infiltration region 130 (the depth of the infiltration region 130 in the stacking direction) can be, for example, greater than or equal to the fiber diameter of the filler of the nonwoven fabric, and is specifically 5 μm or more. , 30 μm or more, or 50 μm or more. As a result, the anchor effect can be enhanced, so the mechanical strength of the composite material 100 can be improved. The upper limit of the penetration depth is not particularly limited. It may be 2T or less, or 1/2T or less.

In addition, the nonwoven fabric in the wall portion 112 may have a structure in which a plurality of fiber fillers are randomly oriented as shown in FIG. can. As a result, compared to the case where the orientation of the fiber filler is random, it is possible to suppress variations in the penetration depth of the penetration region 130 .

The interface between the wall portion 112 of the core member 110 and the support plate member 122 (or the interface between the infiltration region 130 and the non-infiltration region) is inside the stacking direction in the cross-sectional view of FIG. It can have an uneven shape toward it. Specifically, the cross-sectional shape of the upper surface 118 of the wall portion 112 can be uneven. Thereby, it is possible to further increase the interface strength between the wall portion 112 and the support plate member 122 .

In addition, the permeation region 130 may be formed entirely from the left end side to the right end side of the wall portion 112 in cross-sectional view, or may be formed over the entire upper surface 118 of the wall portion 112 in top view. Also good. By enlarging the infiltration region 130 in the depth direction and the plane direction, it is possible to further increase the interface strength between the wall portion 112 and the support plate member 122 .

In this embodiment, a seepage region 130 is formed inwardly from the upper surface 118 of the wall portion 112 and a seepage region (not shown) is formed inwardly from the lower surface 116 of the wall portion 112 . may By forming the seepage regions 130 on both sides of the wall portion 112 of the core member 110, the mechanical strength of the core member 110 can be further increased.

The wall portion 112 can be composed of a molded article of a papermaking body containing the fiber filler and the binder resin. In the nonwoven fabric in the paper product, the fiber fillers are bound together by the binder resin. Thereby, the mechanical strength of the wall portion 112 can be improved. Moreover, by using a papermaking method, which is a method of producing a papermaking body, the core member 110 having various shapes and three-dimensional shapes in plan view and the wall portions 112 constituting the core member 110 can be realized.

Also, the wall part 112 may have a foam structure. That is, the wall portion 112 may be made of foam having a foam structure. Thereby, the weight reduction in the core member 110 can be further enhanced.

The foam structure of the foam may have a closed cell structure or an open cell structure. In the foam of the present embodiment, from the viewpoint of the balance between strength and rigidity, the whole may have a closed cell structure, and from the viewpoint of the balance between strength, rigidity and weight reduction, a closed cell structure and a part It may have an open cell structure.
In the present embodiment, the closed cell structure means a structure having a plurality of spaces (cells) isolated from the outside by a cured thermosetting resin. In such a closed-cell structure, it is possible to realize a structure excellent in airtightness because gas is prevented from passing between the adjacent spaces.

The above-mentioned foam may be wholly or partly composed of a foamed sheet product (a sheet product containing thermally expandable microcapsules). In the present embodiment, from the viewpoint of production stability, it is preferable that the foam as a whole be formed of a foamed sheet product (foam molded product).

The foamable paper product and foam molded product of the present embodiment will be described below.
<Expandable paper product>
FIG. 2 is a schematic perspective view showing an example of the expandable paper product 10 of this embodiment.
The foamable paper product 10 of the present embodiment is a paper product in which the thermally expandable microcapsules C are dispersed.

Here, in the present specification, the term "paper product" is generally used as a technical term indicating the state of a product obtained by using a method of making a fiber material. The state of this product is described, for example, in Patent Publication 1 (Japanese Patent No. 4675276) and Patent Publication 2 (Japanese Patent No. 5426399). According to the document, the paper product refers to the solid content in a wet state remaining on the filter after the liquid content has been dewatered from the raw material slurry in which raw materials such as fibers and resins are dispersed in a dispersion medium. ing. The term "wet state" as used herein means an uncured state before heat treatment, that is, an uncured state before post-curing.

In the present embodiment, the foamable paper product 10 may be in the form of a sheet, or may be in a three-dimensional shape processed into a shape that imitates the shape of a desired molded product (that is, in the form of a preform). Then, by performing foam molding such as heat treatment on the foamable paper product 10, a molded product (expanded molded product 50) can be obtained. This foam molded product 50 is a cured product of the foamable paper product 10 .

The expandable paper product 10 according to the present embodiment is obtained by a paper making method.
As shown in FIG. 2, the expandable paper product 10 obtained by the paper making method has structural features 1 to 3 in terms of the following points.
(Feature 1) The fiber filler B and the thermally expandable microcapsules C are randomly oriented in a plan view of the surface of the foamable paper product 10 .
(Feature 2) In a cross-sectional view in the thickness direction of the expandable paper product 10, the orientation state of the fiber filler B is highly controlled, and the fiber filler B is oriented in a specific direction. In other words, the fiber filler B is laminated in the thickness direction of the expandable paper product 10 .
(Feature 3) The fiber fillers B are bound together by the binder resin A.
Thus, in the expandable paper product 10 shown in FIG. 2, the binder resin A, the fiber filler B, and the thermally expandable microcapsules C are randomly entangled in the surface direction, and such surface structures overlap in the thickness direction. It has a papermaking structure like this.

Also, the foamable paper product 10 can be molded into a desired shape by a foaming process and used as a material for obtaining a foam molded product 50 shown in FIG.
The resin in the foamable paper product 10 is not completely cured, for example, in a B-stage state. Therefore, the expandable paper product 10 can be deformed into another shape. By heating the foamable paper product 10 at the curing temperature of the binder resin A, which is a thermosetting resin, the resin is foamed and completely cured to obtain the foamed molded product 50 .

Next, components constituting the expandable paper product 10 will be described.
(Binder resin A)
The binder resin A is not particularly limited as long as it functions as a binding agent that connects between the fiber fillers B, but for example, a thermosetting resin can be used.
Examples of the thermosetting resin include phenol resin, epoxy resin, unsaturated polyester resin, melamine resin, and polyurethane. These resins can be appropriately selected and used as required, and one type may be used alone, or two or more types may be used in combination.
From the viewpoint of mechanical properties and heat resistance, it is preferable to use at least one of phenol resin and epoxy resin. Moreover, it is preferable to use a phenol resin from the viewpoint of coexistence of weight reduction and high strength.

The thermosetting resin may have a granular or powdery form. This makes it possible to more effectively improve the strength of the foamed molded article 50 obtained by foaming and curing the expandable papermaking article 10 . Although the reason for this is not clear, when the foamable sheet material 10 is heated and pressurized to foam, the thermosetting resin having a granular or powdery shape improves the impregnating property at the time of melting, and the fiber filler B It is presumed that this is because the interface with the thermosetting resin is formed satisfactorily.

As the thermosetting resin, for example, one having an average particle size of 500 μm or less and being in a solid state at room temperature can be used. Thereby, in the manufacturing process of the expandable paper product 10, the thermosetting resin can be more easily formed into an aggregated state. In addition, in the manufacturing process of the expandable paper product 10, from the viewpoint of obtaining a varnish-like material composition, the average particle size of the thermosetting resin is more preferably 1 nm or more and 300 μm or less.
A thermosetting resin having such an average particle size can be obtained, for example, by performing pulverization using an atomizer pulverizer or the like.
The average particle size of the thermosetting resin can be obtained by using a laser diffraction particle size distribution measuring device such as SALD-7000 manufactured by Shimadzu Corporation to obtain the 50% particle size based on mass as the average particle size. can be done.

The thermosetting resin contained in the foamable paper product 10 is preferably in a semi-cured state. The semi-cured thermosetting resin is completely cured in the step of foaming into a desired shape by heating and pressurizing after manufacturing the foamable sheet 10 and molding it. As a result, the foam molded article 50 having an excellent balance between high strength and light weight can be obtained.

(Fiber filler B)
The fiber filler B is obtained by cutting a fiber thread or a long fiber bundle into a predetermined length.
The average fiber length of the fiber filler B is, for example, 0.1 mm or more, preferably 1 mm or more from the viewpoint of obtaining a special structure by papermaking, and for example, 2 mm or more, preferably 2.5 mm from the viewpoint of obtaining mechanical strength. 3 mm or more, more preferably 3 mm or more. On the other hand, from the viewpoint of obtaining good dispersibility, it is preferably 20 mm or less, more preferably 15 mm or less, and even more preferably 12 mm or less.

Examples of the fiber filler B include carbon fiber, glass fiber, metal fiber, ceramic fiber, wholly aromatic polyamide (aramid), wholly aromatic polyester, wholly aromatic polyesteramide, wholly aromatic polyether, wholly aromatic polycarbonate, Wholly aromatic polyazomethine, polyphenylene sulfide (PPS), poly(para-phenylenebenzobisthiazole) (PBZT), polybenzimidazole (PBI), polyetheretherketone (PEEK), polyamideimide (PAI), polyimide, polytetra fluoroethylene (PTFE), poly(para-phenylene-2,6-benzobisoxazole) (PBO), and the like. These fiber fillers B can be appropriately selected and used as necessary, and one type may be used alone, or two or more types may be used in combination.

Furthermore, from the viewpoint of achieving a balance between weight reduction and strength, inorganic fibers may be used, preferably glass fibers and carbon fibers may be used. From the viewpoint of strength and rigidity, it is preferable to use carbon fiber. Moreover, when glass fibers are used, those subjected to aminosilane treatment may be used. Aminosilane treatment is performed by impregnating glass fibers with a solution of an amino group-containing silane coupling agent, or by coating glass fibers with a solution of an amino group-containing silane coupling agent.

Examples of amino group-containing silane coupling agents include N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyl methyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β -aminoethyl)-γ-aminopropylmethyldiethoxysilane and other amino group-containing alkoxysilanes, and hydrolysates thereof. One of these amino group-containing silane coupling agents may be used alone, or two or more thereof may be used in combination.

From the viewpoint of increasing the strength, the content of the fiber filler B may be, for example, 10% by weight or more, or 20% by weight or more, relative to the binder resin A (thermosetting resin). Further, from the viewpoint of achieving a balance between strength and weight reduction, the binder resin A (thermosetting resin) may be, for example, 80% by weight or less, 75% by weight or less, or 70% by weight or less. Well, it may be 50% by weight or less.

(Thermal expandable microcapsules C)
The thermally expandable microcapsules C are particles obtained by microencapsulating a volatile liquid foam material with a thermoplastic shell polymer having gas barrier properties. The thermally expandable microcapsules C function as a foaming material through the following mechanism. That is, the heating softens the outer shell of the capsule, while vaporizing the liquid foam contained in the capsule and increasing the pressure. As a result, the particles are expanded to form hollow spherical particles (expanded particles of thermally expandable microcapsules C).

Examples of the liquid foaming material include low-boiling hydrocarbons such as isopentane, isobutane, and isopropane.
Examples of the thermoplastic shell polymer include polyacrylonitrile, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-methyl methacrylate copolymer, vinylidene chloride-ethyl methacrylate, acrylonitrile-methyl methacrylate copolymer, acrylonitrile-ethyl methacrylate, and the like. mentioned. These may be used alone or in combination of two or more.

As the thermally expandable microcapsules C, commercially available products such as Expancel (manufactured by Nippon Philite Co., Ltd.), Microsphere F50, Microsphere F60 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), and Advancel EM (manufactured by Sekisui Chemical Co., Ltd.) are available. products can be used.

The content of the thermally expandable microcapsules C may be 0.05% by weight or more, or 0.1% by weight, relative to the binder resin A (thermosetting resin) from the viewpoint of lowering the density of the foam molded article 50. % or more. In addition, from the viewpoint of exhibiting an appropriate strength of the foam molded article 50, it may be 10% by weight or less or 5% by weight or less with respect to the binder resin A (thermosetting resin).

In addition to the components described above, the foamable paper product 10 in the present embodiment can contain components such as pulp, a flocculating agent, and various additives.

(pulp)
The expandable paper product 10 of the present embodiment may contain pulp. Pulp is a fibrous material having a fibril structure and is different from the fibrous filler B described above. Pulp can be obtained, for example, by mechanically or chemically fibrillating fibrous materials.
At the time of manufacturing the expandable paper product 10, by paper-making the pulp together with the binder resin A, the fiber filler B, and the thermally expandable microcapsules C, these can be more effectively agglomerated, resulting in more stable foaming. It becomes possible to realize the production of the elastic paper product 10.

Examples of the pulp include cellulose fibers such as linter pulp and wood pulp, natural fibers such as kenaf, jute and bamboo, para-type wholly aromatic polyamide fibers (aramid fibers) and copolymers thereof, aromatic polyester fibers, poly Examples include fibrillated organic fibers such as benzazole fibers, meta-aramid fibers and their copolymers, acrylic fibers, acrylonitrile fibers, polyimide fibers and polyamide fibers. One type of pulp may be used alone, or two or more types may be used in combination.

The pulp content may be 0.5% by weight or more, 1% by weight or more, or 2% by weight or more relative to the binder resin A (thermosetting resin). As a result, aggregation of the thermosetting resin during papermaking can be more effectively generated, and more stable production of the expandable papermaking body 10 can be realized. On the other hand, the pulp content may be 10% by weight or less, 8% by weight or less, or 5% by weight or less relative to the binder resin A (thermosetting resin). This makes it possible to improve the mechanical properties and thermal properties of the foam molded article 50 more effectively.

(coagulant)
The expandable paper product 10 of the present embodiment may contain a flocculating agent. The aggregating agent has a function of aggregating the binder resin A, the fiber filler B, and the thermally expandable microcapsules C into flocs during the production of the expandable sheet product 10 . Therefore, more stable production of the expandable paper product 10 can be achieved.

Examples of the flocculant include cationic polymer flocculants, anionic polymer flocculants, nonionic polymer flocculants, and amphoteric polymer flocculants. More specific examples include cationic polyacrylamide, anionic polyacrylamide, Hoffmann polyacrylamide, Mannick polyacrylamide, amphoteric copolymer polyacrylamide, cationized starch, amphoteric starch, and polyethylene oxide. These flocculants may be used singly or in combination of two or more. Moreover, in the flocculant, the polymer structure, molecular weight, amount of functional groups such as hydroxyl groups and ionic groups, etc. can be adjusted according to the required properties.

The content of the aggregating agent may be 0.01% by weight or more, 0.05% by weight or more, or 0.1% by weight or more relative to the binder resin A (thermosetting resin). Thereby, in the production of the expandable paper product 10, the yield can be improved. On the other hand, the content of the aggregating agent may be 1.5% by weight or less, 1% by weight or less, or 0.5% by weight or less relative to the binder resin A (thermosetting resin). As a result, in the production of the expandable paper product 10 using the paper making method, dehydration treatment and the like can be performed more easily and stably.

The foamable paper product in the present embodiment can further contain various additives for the purpose of adjusting production conditions and expressing required physical properties. Examples include thermoplastic resins, inorganic powders for improving properties, metal powders, stabilizers such as antioxidants and UV absorbers, flame retardants, release agents, plasticizers, resin curing catalysts and curing accelerators, and pigments. , dry strength improvers, wet strength improvers, yield improvers, drainage improvers, size fixers, rosin sizing agents for acidic papermaking, rosin sizing agents for neutral papermaking, alkyl Sizing agents such as ketene dimer-based sizing agents, alkenylsuccinic anhydride-based sizing agents, special modified rosin-based sizing agents, and coagulants such as aluminum sulfate, aluminum chloride, polyaluminum chloride, and the like.

The foamable paper product 10 of the present embodiment may contain aramid microfibers as an additive. This makes it possible to improve the handleability of the dried foamed paper product 10 .

<Method for producing expandable paper product>
FIG. 3 is a process cross-sectional view showing the manufacturing process of the expandable paper product 10. As shown in FIG.
In the method for producing the expandable paper product 10 of the present embodiment, the binder resin A, the fiber filler B, and the thermally expandable microcapsules C are mixed, and then the mixture is made into a paper by a paper making method to produce the expandable paper product 10. a step of obtaining Here, the paper-making method is a method using a paper-making technique, which is one of paper-making techniques as shown in FIG. 3(b).

Hereinafter, the method for producing the expandable paper product 10 by the wet paper making method will be described in detail with reference to FIG. 3 .

First, as shown in FIG. 3(a), a binder resin A, a fiber filler B, and a thermally expandable microcapsule C are added to a solvent and stirred, mixed, and dispersed. At this time, among the components described above, other components than the flocculant may be added to the solvent. Thereby, a varnish-like material composition (slurry) for forming the foamable paper product 10 can be obtained.

A method for dispersing each component in a solvent is not particularly limited, but an example thereof includes a method of stirring using a disperser.

The solvent is not particularly limited. From the viewpoint of suppressing the increase in energy due to the boiling point of 50° C. or more and 200° C. or less, it is preferable.
Examples of the solvent include water, alcohols such as ethanol, 1-propanol, 1-butanol and ethylene glycol, ketones such as acetone, methyl ethyl ketone, 2-heptanone and cyclohexanone, ethyl acetate, butyl acetate, methyl acetoacetate, Esters such as methyl acetoacetate, and ethers such as tetrahydrofuran, isopropyl ether, dioxane, furfural, and the like can be mentioned. These solvents may be used alone or in combination of two or more. Among these, it is more preferable to use water because it is abundantly supplied, inexpensive, has a low environmental load, is highly safe and is easy to handle.

Subsequently, a flocculant may be added to the resulting slurry. This makes it easier to obtain aggregates F in which the binder resin A, the fiber filler B, and the thermally expandable microcapsules C are aggregated in the form of flocks (FIG. 3(b)).

Subsequently, the slurry obtained by mixing the binder resin A, the fiber filler B, the thermally expandable microcapsules C, and the like is made into paper through a filter, whereby the foamable paper product 10 can be obtained.

Specifically, as shown in FIG. 3B, the above slurry is introduced into a container provided with a sheet-like mesh 30 (filter) on the bottom surface. Then, the solvent in the slurry is passed through the mesh 30 and discharged out of the container, and the aggregates F in the slurry remain on the mesh 30 (filter). Thereby, the aggregate F and the solvent can be separated from each other.
Here, by appropriately selecting the shape of the mesh 30, it is possible to adjust the shape of the resulting expandable paper product.
After that, the aggregates F obtained on the filter (mesh 30) may be placed in a drying oven, for example, to be dried to further remove the solvent remaining in the aggregates F.
As described above, the foamable paper product 10 shown in FIG. 3(c) is manufactured.

In this embodiment, in the surface direction of the expandable paper product 10 (formed along the surface direction of the filter) by the paper making method as shown in FIG. It is thought that random and moderately entangled structures can form a papermaking structure in which the foamable papermaking bodies 10 are laminated in the thickness direction. As a result, a large amount of the fiber filler B can be mixed in, and the foamable paper product 10 having an excellent balance between weight reduction and strength can be obtained.
Further, by using the papermaking method, the dispersion of the thermally expandable microcapsules C in the foamable paper product 10 can be enhanced.

Moreover, the filter used in the papermaking method may be flat as shown in FIG. 3(b), or may be three-dimensional. A three-dimensional foamable paper product 10 can be formed by a papermaking method using a three-dimensional filter (hereinafter referred to as a three-dimensional papermaking method). Accordingly, by using the three-dimensional papermaking method, the core member 110 having a three-dimensional shape can be easily realized.

In addition, in the papermaking method, a method of forming the foamable papermaking body 10 in a part of the region A on the surface of the filter and not forming the foaming papermaking body 10 in the other region B (hereinafter referred to as a multicolor papermaking method) ) may be adopted. By using the multicolor papermaking method, it is possible to adjust the region (shape in top view) in which the expandable papermaking body 10 is formed. In the multi-color papermaking method, for example, a means for papering the slurry with a filter while providing a covered area and an uncovered area where the filter surface is not covered with a mask or the like, or a suction area for sucking the slurry and a non-sucking area for the back surface of the filter. A means for making the slurry through a filter while providing a non-sucking area can be used.
According to this embodiment, it is possible to appropriately control the shape of the wall portion 112 when viewed from above by adjusting the forming region of the expandable paper product 10 in the multicolor paper making method.

In the above-described multicolor papermaking method, the expandable papermaking body 10 can be configured to have voids in the portion corresponding to the region B. That is, the foamable paper product 10 having a perforated structure can be formed. In this case, it is possible to use the expandable paper product 10 in the portion corresponding to the region A as the wall portion 112 and use the void in the portion corresponding to the region B as the lightweight portion 114 . The light weight portion 114 in the core member 110 may consist of voids. Thereby, weight reduction can be improved.
By removing a predetermined region of the expandable paper product 10 by cutting means or the like, the expandable paper product 10 having the lightweight portion 114 having a desired shape such as a perforated structure can be realized.

Moreover, the multicolor papermaking method can be repeatedly carried out a plurality of times. Each time the multicolor papermaking method is carried out, the area on the filter forming the foamable papermaking body 10 can be appropriately changed. Thereby, it is possible to realize the expandable sheet product 10 including at least the expandable sheet product A and the expandable sheet product B having different thicknesses and composition conditions in the plane or in the stacking direction.
In this case, between the expandable sheet product A and the expandable sheet product B, an entangled region can be formed in which the respective fiber fillers are entangled with each other. When the expandable paper product A is used for the wall portion 112 and the expandable paper product B is used for the lightweight portion 114, in the core member 110, the fiber filler in the wall portion 112 and the foamed member constituting the lightweight portion 114 A entangled region is formed in which the fiber fillers are entangled with each other. Thereby, the mechanical strength of the core member 110 can be improved.

For example, by repeatedly performing the multicolor papermaking method using slurries with different composition conditions such as the content of the thermally expandable microcapsules C, the sheet members (holes) of the expandable papermaking body 10 having different compositions and structures in the plane A sheet-like foamable paper product 10) having no perforated structure can be formed. Also, by changing the papermaking conditions in the multicolor papermaking method, it is possible to form the sheet members of the expandable papermaking body 10 having different thicknesses in the plane. It is possible to adjust the expansion rate of the foam molded article 50 according to the content and thickness of the thermally expandable microcapsules C. In the foamable paper product 10 , the portion where the content of the thermally expandable microcapsules C is small and the portion where the thickness is thin can be used as the lightweight portion 114 . The lightweight portion 114 in the core member 110 may be partially or wholly made of a foam material having a higher foaming rate than the wall portion 112 . Thereby, mechanical strength and weight reduction can be improved.

In addition, you may use the above papermaking methods in combination suitably.
Moreover, the paper product having no foam structure and its production method can be the same as the above-mentioned foamable paper product and its production method, except that the thermally expandable microcapsules C are not contained.

<Foam molding>
The foamed molded article 50 of the present embodiment is a molded article of the expandable papermaking article 10, and has a cell structure in which cells D formed by foaming the thermally expandable microcapsules C are dispersed in the molded article.

<Method for producing foam molded product>
In the method for producing the foam molded article 50 of the present embodiment, a slurry is prepared by mixing a binder resin A (thermosetting resin), a filler (fiber filler B), and a thermally expandable microcapsule C, and the slurry is made into paper. a step of obtaining an expandable paper product 10 by
The expandable paper product 10 is arranged in a part of the inside of the molds 40, 41, and the thermally expandable microcapsules C are expanded to expand the expandable paper product 10 to the entire inside of the molds 40, 41. Thus, it is possible to include a step of obtaining a foam (foam molding 50) composed of a molding of the foamable papermaking product 10.

FIG. 4 is a cross-sectional schematic diagram showing an example of the method for producing a foam according to this embodiment.
Hereinafter, a method for manufacturing the foam molded article 50 will be described in detail with reference to FIG. 4 .

First, as shown in FIG. 4(a), the foamable paper product 10 is placed inside molds 40 and 41 (mold cavities). At this time, the volume of the mold cavity composed of the mold 40 and the mold 41 is assumed to be larger than the volume of the expandable paper product 10 . As a result, the foamable paper product 10, which is the raw material, can be placed in a state in which the insides of the molds 40 and 41 are not completely filled, that is, in a so-called short shot. This mold cavity can be appropriately set according to the shape of the foamable paper product 10 .

Next, foam molding is performed on the foamable paper product 10 . For example, as shown in FIG. 4(b), the thermally expandable microcapsules C are expanded by heat treatment to expand the expandable paper product 10. As shown in FIG. The expanded foamable paper product 10 will fill the entire mold cavity. At this time, the expandable paper product 10 is molded by the internal pressure (stress from the molds 40 and 41) due to the foaming of the thermally expandable microcapsules C, and the foam molded product 50 is obtained. Thereby, it is possible to mold the foam molded body 50 having a predetermined shape.
In the foam molding process described above, the curing reaction of the binder resin A proceeds, and a matrix resin having a three-dimensional structure (resin cured body having a three-dimensional network structure) is formed in the foam molded body 50 . Also, the thermally expandable microcapsules C are expanded by the heat treatment described above to form air bubbles D (hollow spherical particles).
Thus, the foam molded article 50 of the present embodiment can be produced by the short shot method. By using the short shot method, the foaming pressure generated by expanding the cells of the thermally expandable microcapsules C can be used to form the foamable paper product 10 .

The heat treatment is not particularly limited, but may be, for example, about 160 to 250° C. for about 10 to 30 minutes. In the method of manufacturing the foam molded article 50 of the present embodiment, no external molding pressure is applied, but the internal pressure in the molds 40 and 41 is, for example, approximately 1.5 to 5 MPa.

Here, an injection molding method or the like can be mentioned as a method of applying molding pressure from the outside. In this method, the filling pressure and the holding pressure caused the thermally expandable microcapsules to be unable to foam and the cells to be destroyed.
On the other hand, in the method for producing the foamed molded article 50 of the present embodiment, since molding pressure is not applied from the outside, it is possible to sufficiently suppress unfoaming of the thermally expandable microcapsules C and breakage of the cells D. .

(Manufacturing method of composite material 100)
The composite material 100 of this embodiment can include laminating the core member 110 and the support plate member 120 . As a lamination method, the core member 110 and the support plate member 120 may be joined by applying heat or pressure, or they may be joined via an adhesive layer.
Also, when the support plate members 120 and 122 are laminated on both sides of the core member 110, they may be joined together.

When the wall portion 112 of the core member 110 is composed of the foam molded body 50, a support plate member is arranged on the lower surface of the foamable papermaking body 10 in the molding space in the molds 40 and 41 shown in FIG. 4(a). The foam molding can be carried out in this state, or in a state in which the support plate member is arranged on each of the upper surface and the lower surface of the expandable paper sheet 10 . This allows a foam structure to be formed in the wall portion 112 and allows the core member 110 and the support plate members 120, 122 to be joined together.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can also be adopted.
Examples of reference forms are added below.
1. a core member having a layered structure;
A composite material comprising a support plate member laminated on one surface of the core member and made of a fiber-reinforced resin material in which reinforcing fibers are impregnated with a resin,
The core member has a wall portion and a light portion having a smaller specific gravity than the wall portion,
The wall portion has a nonwoven fabric composed of a plurality of fiber fillers from the one surface of the core member to the other surface opposite to the one surface, and
A composite material comprising an impregnated region in which a portion of the resin in the fiber-reinforced resin material impregnates the nonwoven fabric of the wall.
2. 1. A composite material according to
The composite material, wherein the penetration depth of the penetration region is 5 μm or more.
3. 1. or 2. A composite material according to
The composite material, wherein an interface between the core member and the support plate member has an uneven shape toward the inside in the stacking direction.
4. 1. to 3. A composite material according to any one of
The composite material, wherein the wall portion has a nonwoven fabric in which a plurality of fiber fillers are oriented substantially parallel to the one surface of the core member.
5. 1. to 4. A composite material according to any one of
A composite material in which the plurality of fiber fillers in the wall portion are randomly oriented in a cross-sectional view parallel to the one surface of the core member.
6. 1. to 5. A composite material according to any one of
A composite material, wherein the light weight portion in the core member comprises a space defined by the wall portion.
7. 1. to 6. A composite material according to any one of
A composite material, wherein the light weight portion is composed of voids or a foamed portion.
8. 1. to 7. A composite material according to any one of
A composite material, wherein the wall has a foamed structure.
9. 1. to 8. A composite material according to any one of
A composite material in which the wall portion is composed of a molded article of a papermaking body containing the fiber filler and the binder resin.
10. 9. A composite material according to
A composite material, wherein the binder resin comprises a phenolic resin.
11. 1. to 10. A composite material according to any one of
A composite material, wherein the resin in the fiber-reinforced resin material comprises an epoxy resin.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to the description of these Examples.

The materials listed in Table 1 are as follows.
(Thermosetting resin)
Thermosetting resin 1: Phenol resin (manufactured by Sumitomo Bakelite Co., Ltd., PR-51723)
(Foam material)
Foaming material 1: thermally expandable microspheres (manufactured by Sekisui Chemical Co., Ltd., Advancel (registered trademark) EM-304)
(Additive)
Additive 1: Aramid microfiber (manufactured by Daicel Finechem, Tiara)
(fiber filler)
Fiber filler 1: Carbon fiber (manufactured by Toho Tenax, HTC110, average fiber length: 6 mm)

The raw material volume fraction after foam molding of the foam material in Table 1 indicates the volume porosity of the foam.

<Example 1>
(Preparation of foamable paper product)
First, the raw material components shown in Table 1 (thermosetting resin pulverized to an average particle size of 50 μm (50% particle size based on mass) with an atomizer pulverizer, fiber filler, foaming material, and additives) are shown in Table 1. It was added to water at a mixing ratio (raw material volume fraction [Vol %] after foam molding) and stirred for 10 minutes with a disperser to obtain a mixture. Here, 10000 parts by weight of water was added to a total of 100 parts by weight of constituent materials consisting of a thermosetting resin, a fiber filler, a foaming material and an additive.
Next, 0.2% by weight of a solution prepared by dissolving 800 ppm of polyethylene oxide (PEO) as a fixing agent (aggregating agent) in water is added to the total of the constituent materials described above, and the constituent materials are flocculated. agglomerated to
(Papermaking process)
Subsequently, the resulting aggregates were separated from water with a 30-mesh metal mesh (paper making). After that, the sheet-making layer remaining on the metal mesh was dehydrated and pressed at room temperature at 1 MPa, and dried in a drier at 70° C. for 5 hours to obtain a plate-like foamed sheet-making body.
(Production of composite material)
Thickness: 0.5 mm CFRP (B-stage prepreg made by impregnating glass cloth with epoxy resin), the resulting foamed paper product with a thickness of 3.5 mm, in this order of lamination, a mold with a predetermined thickness These are collectively heat-treated at 180° C. for 10 minutes at an internal mold pressure of 10 MPa, and foamed by the short shot method to form an expandable paper product (core member). A "composite material" in which a CFRP cured product (supporting plate member) was laminated on one surface of the sheet was produced. The specific gravity of the resulting composite material was 0.36 (specific gravity of core member: 0.2, specific gravity of support plate member: 1.5).

<Comparative Example 1>
Thickness: 0.5 mm CFRP (B-stage prepreg made by impregnating glass cloth with epoxy resin, the same as that used in Example 1), Thickness: 3.5 mm PEI (polyetherimide) foam are stacked in this stacking order in a mold with a predetermined thickness, and they are collectively subjected to heat treatment at 180 ° C. for 10 minutes at an internal mold pressure of 10 MPa, and compression molding is performed to form a PEI foam. A “composite material” was produced in which a CFRP cured product (supporting plate member) was laminated on one surface of the (core member). The specific gravity of the resulting composite material was 0.36 (specific gravity of core member: 0.2, specific gravity of support plate member: 1.5).

The obtained composite material was evaluated based on the following evaluation items.

(cross-section observation)
The obtained "composite material" is cut in the direction of lamination of the support plate member, the core member and the support plate member, and is cut in the direction orthogonal to the lamination direction. The orientation of the fiber filler was observed with a microscope for X and Y.
- Orientation of Fiber Filler In Example 1, the orientation of the fiber filler was substantially parallel on the cross section X in the stacking direction. On the other hand, on the cross section Y in the orthogonal direction, the orientation of the fiber filler was random.

・Infiltration area In the cut surface X of Example 1, the resin infiltrated into the core member so as to involve the fiber filler, and an infiltration area of about 100 μm in the lamination direction was observed (Fig. 1 ( c)).
On the cut surface X of Comparative Example 1, no seepage region as described above was observed.

(Strength)
Using the obtained composite material, the following test pieces were produced, and using the obtained test pieces, the following bending tests were performed in accordance with ISO178.
・ Specimen thickness: 4 mmt (core member: 3.5 mm, support plate member (CFRP): 0.5 mm)
・ Specimen shape: 80 mm × 10 mm
・Bending direction: Stress applied from the core member side (CFRP on the outside of the bend)

As a result of the bending test, the bending strength of Example 1 was higher than the bending strength of Comparative Example 1. Regarding the failure mode, in Example 1, internal failure of the core member (a state in which a part of the core member was peeled off and adhered to the CFRP side) was observed, while in Comparative Example 1, interfacial failure (a core member on the CFRP) was observed. no adhesion) was observed.

(Lightweight)
A "composite material" having a honeycomb-structured core member was obtained in the same manner as in Example 1, except that the following (processing of the foamable paper product) was added.
(Processing of foamable paper product)
The “plate-like foamable paper product” obtained in the above (paper making process) is subjected to cutout processing under the conditions of six hexagonal cutout portions, and the remaining portion (wall portion) has a honeycomb shape when viewed from above. A plate-like perforated foamable paper product was formed. The resulting "plate-like perforated foamable paper product" was used as the foamable paper product in the above step (preparation of composite material).

It was found that the "composite material" of Example 1, in which the core member has the honeycomb structure (the wall portion and the light portion), can be made lighter than the case without the light portion.

It was found that the composite material of Example 1 was superior to Comparative Example 1 in mechanical strength. Moreover, it was found that the composite material of Example 1 can realize a structure excellent in lightness.

REFERENCE SIGNS LIST 10 Expandable paper product 30 Mesh 40 Mold 41 Mold 50 Foam molded product A Binder resin B Fiber filler C Thermally expandable microcapsule D Bubble F Aggregate 100 Composite material 110 Core member 112 Wall portion 114 Lightweight portion 116 Lower surface 118 Upper surface 120 support plate member 122 support plate member 130 seepage region

Claims (11)

a core member having a layered structure;
A composite material comprising a support plate member laminated on one surface of the core member and made of a fiber reinforced resin material in which reinforcing fibers are impregnated with a thermosetting resin,
The core member has a wall portion and a light portion having a smaller specific gravity than the wall portion,
The wall portion has a nonwoven fabric composed of a plurality of fiber fillers from the one surface of the core member to the other surface opposite to the one surface, and
In a cross section in the stacking direction of the core member and the support plate member, part of the thermosetting resin in the fiber-reinforced resin material penetrates into the nonwoven fabric of the wall. and a non-saturated region . A composite material according to claim 1,
The composite material satisfies 4/5T or less when the penetration depth of the penetration region is 5 μm or more and T is the thickness of the core member in the cross section in the stacking direction . A composite material according to claim 1 or 2,
The composite material, wherein an interface between the core member and the support plate member has an uneven shape toward the inside in the stacking direction. A composite material according to any one of claims 1 to 3,
The composite material, wherein the wall portion has a nonwoven fabric in which a plurality of fiber fillers are oriented substantially parallel to the one surface of the core member. A composite material according to any one of claims 1 to 4,
A composite material in which the plurality of fiber fillers in the wall portion are randomly oriented in a cross-sectional view parallel to the one surface of the core member. A composite material according to any one of claims 1 to 5,
A composite material, wherein the light weight portion in the core member comprises a space defined by the wall portion. A composite material according to any one of claims 1 to 6,
A composite material, wherein the light weight portion is composed of voids or a foamed portion. A composite material according to any one of claims 1 to 7,
A composite material, wherein the wall has a foamed structure. A composite material according to any one of claims 1 to 8,
A composite material in which the nonwoven fabric of the wall portion is formed of a molded article of a papermaking body containing the fiber filler and the binder resin. A composite material according to claim 9,
A composite material, wherein the binder resin comprises a phenolic resin. A composite material according to any one of claims 1 to 10,
A composite material, wherein the thermosetting resin in the fiber-reinforced resin material comprises an epoxy resin.

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